Electrical muffle or heater



(No Model.) 1 2 sheets-sheet 1.- L. E. OUSTER. ELECTRICAL MUFFLE 0RHEATER.

Patented Oct. 20, 1896.

2 Sheets-Sheet 2.-

L. E. GUSTBR. ELECTRICAL MUFFLE 0R HEATER.

No. 569,911. Patented Oct. 20, 1896.

(N0 Mbdel.)

WITNESSES zwrzwzofe MM. QMGBW- MW LEVITT E. ous'rnn,

PATENT rricn.

OF DAYTON, OHIO.

ELECTRICAL MUFFLE OR HEATER.

SPECIFICATION forming part of Letters Patent No. 569,911, dated October20, 1896. Application filed May 31,1895. Serial No. 551,034. (No model.)

To all whom it may concern:

Be it known that I, LEVITT E. CUSTER, of Dayton, in the county ofMontgomery and State of Ohio, have invented certain new and usefulImprovements in Electrical Muf'fies or Heaters; and I do herebydeclarethat the following is a full, clear, and exact descriptionthereof, reference being had to the accompanying drawings, and to theletters of reference marked thereon, which form part of thisspecification.

The object of this invention is to provide an electrical heater ormuffle especially designed for use by dentists in the manufacture ofporcelain dental plates; and the invention embraces the importantfeatures of the muffies disclosed in my applications for Letters Patent,Serial Nos. 532,646 and 532,647, filed December22, 1894, and certainotherimprovements also.

The invention consists, first, in a quick and powerful electrical heaterproduced by substantially covering the entire inner surface or walls oftheheating-chamber with resistance-wires; second, in utilizing theheating-wires in the muffle as a rheostat to regulate the temperatureand the initial heating of the muffle; third, in improved switch devicesfor shifting the current through the resistances in the muffle in seriesor multiple; fourth, in the novel construction or-arrangement ofsight-openings in the muffle, whereby the proper heating or fusion ofthe substance being treated can be readily determined by reflection oflight through said openings.

The invention is summarized in the claims, and the best form of mufflenow known to me is constructed substantially as shown in the drawingsand hereinafter described in detail.

In said drawings, Figure l is a front View of the muffle; Fig. 2, a planView; Fig. 3, a vertical section on line 3 3, Fig. 2'; Fig. 4, a bottomplan View with switch off in dotted lines and shifted to throw theresistances in series in full lines. Fig. 5 is a similar view withswitch shifted to throw resistances in multiple. Fig. 6 is a detailtransverse section through the switch lever and button on line '6 6,Fig. 5. Fig. '7 is a detail vertical section 011 line 7 7, Fig. 1.

The muflie consists of upper and lower parts A B, which are closelyfitted together and internally lined with refractory material, such asfire-clay. In each part is a cavity a Z), which when the parts arefitted together constitute the heating-chamber. Part B is mounted on aninsulating-base D, of suitable material, on which are two binding-postsd d, to which are connected wires Z, leading to a battery 2 or othersuitable current-generator, with which the muffie is in circuit. Theentire inner surface or walls of each cavity a b is substantiallycovered with serpentine layers of platinum wire or other suitable highresistance not liable to buckle or fuse at the temperature requisite tofuse porcelain. This resistance is preferably embedded in the walls ofthe cavities just sufficiently to hold it in position and preventshort-circuiting, while allowing the greatest amount of heat to escapeby conduction, convection, and radiation into the chamber of the muffle.

It will be noted that the-resistances substantially cover everyportion-top, bottom, and sidesof the chamber in the muffie, and thiscomplete envelopment of the walls with high-resistance wires I claim asnew and of the utmost importance in dental work and for fusingporcelain. I also preferably employ platinum wire as most free frombuckles and capable of withstanding a temperature greater than isnecessary to fuse porcelain.

As the fusing-points of high-fusing porcelain and of platinum are nearlythe same, the inner surface of the muffie should be covered with theplatinum wire as compactly arranged as is possible, while preventing ashort circuit between adjoining portions of the wire, so that anindividual strand of wire will not have to be so highly heated whenthere are many of them in a given area as it would be if there werefewer-or more distantly separated strands. By having the wires so closetogether as to present an almost solid radiating-surface more heat willbe developed in the muffle with less danger to the wire.

I am aware that portions of the walls of chambers in muffles and heatershave been covered with resistance, and I disclaim such, as they producean unequal heating effect in the chamber.

By having every part of the chamber-walls covered with heating wires thegreatest amount of heat and equality of temperature is attained in themuffle, since there will be no unprotected parts of the walls where theheat will be lost by conduction. This complete envelopment of themuffle-chamber in heating-wires I consider a very important feature ofthe invention.

The ends of the resistance a in part A are connected to contacts cc,projecting through the wall of said part and respectively contactingwith upstanding spring-conductors E E, attached to the base D, as shown.One end, N, of the resistance 1) in part b is connected to post (I, andthe other end, Z), is connected to a contact-plate F, fastened to theunder side of base D. Spring E is connected by a wire E to acontact-plate G, fastened to the under side of base D near plate F, andspring E is connected by a wire E to the plate F, as shown.

A switch H is pivoted to the under side of base D and is electricallyconnected with post d. Said switch has a contact-arm h, which is adaptedto make contact with plate G or E, if properly shifted, or to breakcontact with both and cut the muffle out of or break the circuit.Attached to this switch is a contact-button I, insulated from the switchby a bushing I, as shown, electrically connected by a flexible oryielding connection 2' to post d. \Vhen arm h contacts plate F, button Iwill contact plate G. The object of this construction is to enable theoperator to employ resistances a I) in series or in multiple and utilizethese resistances as a rheostat in starting up the heater, for in dentalwork it is desirable to subject the plates to a low or slow heat untilthe oven is heated thoroughly and the plates thoroughly dried, and thento use the greater heat to fuse the porcelain, the.

By first connecting resistances a b in series there is a greatresistance to the current and a low heat is obtained. Then by switchingthe current through the resistances in multiple parallel the resistanceis halved and the current passing consequently doubled, greatlyincreasing the temperature. hen switch 11, therefore, is turned so thatarm 7L contacts plate G, the current passes from post (1' to spring Eand through resistance a back to spring E, thence to plate F, thenthrough resistance Z) to post (Z, thus going through resistances a b inseries. hen the switch is turned so as to contact arm h with plate F andbutton I with plate G, the current enters .from post cl through theswitch to plate Gr,

there divides, part passing through resistance 1) to post d, and partpassing through springs E, resistance a, spring E, wire E plate A,button I, and cord 2' to post cl, thus halving the resistance anddoubling the current passing through the muffle.

I do not confine myself to the particular construction herein shown anddescribed, as the principal feature of this part of my invention is theemployment of resistances in a muille or heater with means whereby thecurrent can be sent through the resistances in series or in multiple.

Two sight-openings .l' J are made in opposite sides of the muffle, onepreferably at an angle of about forty-five degrees above the other. Nowit is very difficult to ascertain the exact degree of fusion ofporcelain on a dental plate when looking directly into a muffle througha single opening, as in the old forms. This difficulty I overcome by usng the two openings, as shown, both of which can be quite small. By thisarrangement a ray of light entering one opening will be re flected outthrough the other, and by the amount of reflected light the condition ofthe glaze or fusion of the porcelain can be very readily and accuratelydetermined, As the light is to be reflected from the obgect to be fused,the positions of the openings Wlll depend somewhat upon the objects tobe treated, or the objects must be arranged in the muffle with referenceto the openings. The principal idea is to have the openings in suchrelation to each other and the object being treated (dental plates, as Iemploy the apparatus) that a ray of light entering one opening will bereflected by the object out of the other when at a proper temperature.

The openings might be provided with stopples to confine the heat in thechamber, ex cept when observations are to be made.

Having thus described my invention, what I therefore claim as new, anddesire to secure by Letters Patent thereon, is

1. The herein-described muffle consisting of the two chambered parts A,13, the resistances therein, the insulating-base, the contact-springs,the binding-posts, and suitable means substantially as described wherebythe current maybe caused to traverse the resistances in series ormultiple, substantially as described.

2. The herein-described muffle consisting of the parts A, B, each havingan internal lining of refractory material, a chamber or cavity, and aresistance-coil substantially covering the entire surface of the cavity;the 1nsulating-base, the contact-springs the hinding-posts andelectrical connections between. said posts and the resistances, andsuitable means whereby an electrical circuit may be established throughsaid resistances, substantially as described. 0

An electrical muffle having an interior chamber, electricalheating-wires surroundin g said chamber, and opposite openings throughthe walls of the muffle for the en trance and exit of light, saidopenings being at angles to each other, and all adapted for the purposeand constructed substantially as described.

a. An electrical muffle having an interior chamber, whose top, bottom,and side walls are substantially covered with resistancewires,and havingsubstantially opposite openings in its walls respectively for theadmission of a ray of light, and for the exit of it when reflected,substantially as and for the purpose described.

5. Thecombination of a muflie having a plurality of resistances aroundits heatingchamber, and sight-openings substantially as described; witha switch and electrical connections whereby said resistances may be0011- nected in series or multiple substantially-as described.

G. A muffle having a lower chambered part mounted on an insulating-baseand provided with a resistance-coil; an upper part also chambered andprovided with a resistanceeoil; suitable means substantially asdescribed, whereby a circuit may be established through said resistancesin series or multiple at the will of the operator, and the twosubstantially opposite sight-openings communicatin g with the interiorchamber of the muffle, for the purpose and substantially as described.

connected to said resistances, substantially as described, the binding-posts,and the switch H, carrying contact-button I, and flexibleconnection between said button and one bindingpost, all substantially asand for the purpose set forth.

8. The combination with the two-part muffle, the resistance in eachpart, the insulating base, the springs E, E electrically connected withthe upper resistance; the plates F, connected to spring E, the plate Gconnected to post E and the lower resistance, the bindingposts cl, (2,the connections between the lower resistance and post cl, the switch Hconnected with post d, and the button I on switch I'I connected to postd, all substantially as and for the purpose set forth.

I11 testimony that I claim the foregoing as my own I affix my signaturein presence of two witnesses.

LEVITT E. (DUSTER. Witnesses WILLIAM G. FRIZELL, S. RUDOLPH LIGHT.

